The use of enclosed cargo containers having a rectangular parallelepiped shape has increased greatly in recent years. Such containers are easy to load and unload off carriers such as ships, trucks and cargo vessels. Many ships have been especially adapted to carry such containers. In such ships the cargo holds have frameworks adapted to receive and hold in position the containers while the ship is in transit. This class of vessel is called a container ship.
The cargo container usully come in 40-foot outside lengths with 8-foot outside widths. The outside height of the containers have varying dimensions ranging from about 8 feet to about 9 feet 6 inches. In conventional container storage aboard ships the containers are stowed 3 inches apart head to head and one and one half inches apart laterally. There also is normally about a one inch space between containers when they are stacked vertically. The containers have corner fittings built into each of the four corners of the containers. These corner fittings have openings on the three external faces thereof adapted to receive and removably engage with container interlocks which locks are used to connect the containers together. The locks also provide for uniform spacing between the containers.
A class of container interlocks has been developed to interlock the top corner fittings of horizontally adjacent containers with a rigid bridge affixed to the lock on each of the containers. In such cases the bridge can be an integral part of the fitting or it can be a separate piece which connects up with two or more interlocks. The interlocks of this class of locks are called bridge interlocks. In commercial use there are bridge interlocks which can interlock a top corner fitting of a container having a height of 8 feet with the top corner fitting of a container having a height of 9 feet 6 inches.
There is a large body of merchant ships called bulk carriers. In bulk carriers there are several large holds with no obstructions therein such as posts which would interfere with the onloading and offloading of bulk cargos such as grains, coal, iron ore, etc. At the present time the bulk carrier ships have a very limited utility as container carriers. If a bulk carrier carrying coal to Japan arrives there and offloads the coal it would be very desirable for it to be able to pick up a cargo to deliver in another port. Unfortunately in many instances there is no bulk cargo available for such ships to carry back to its home port or another port. Because of this many times bulk cargo ships must travel unloaded back to its home port. This is both costly and very wasteful of fuel.
To overcome this problem, bulk cargo shippers have tried to carry containers in their vessels. They have tried to employ conventional lashing methods to hold the containers in place. Generally they use a combination of container bridge interlocks and cable lashing to hold the containers in place. The use of such lashings has been time consuming and very costly. Furthermore there have been many accidents at sea due to the improper and inadequate use of such lasings.
The art has been searching out methods whereby bulk carriers can be transformed into container carriers. The general thrust in the art has been to try to improve permanent conventional lashings such as cables which are affixed both to the container and to the body of the ships. Mounts have been welded onto the decks of the holds of such ships to prevent movement of the bottom layer of the containers while the ship is in transit. Ideally to constrain the motion of stacked containers it would be best to employ a constraining apparatus which structurally becomes part of the ship's structure so as to achieve mutual enhancement thereof. Conventional means of lashing does not achieve this desirable result.